1. Technical Field of the Invention
The present invention relates to an electronic control apparatus, which is used by being loaded on vehicles and provided with plural microcomputers.
2. Related Art
As the functions of automobiles (vehicles) become complicated, the number of electronic control apparatuses loaded on a vehicle is more and more increasing. Typical conventional electronic control apparatus have been configured so that each of the plurality of functions of a vehicle is provided with one electronic control unit. To take measure for the increasing number of electronic control units, it has been suggested that the electronic control units be integrated into a single system.
In such an electronic control apparatus with integrated electronic control apparatuses, it is considered that a microcomputer is required for each of the plurality of functions. This is because use of only a single microcomputer will not be sufficient for fully performing the processes for realizing the plurality of functions.
In such an electronic control apparatus with integrated so electronic control apparatuses having a plurality of microcomputers, it is considered that the system may have a configuration in which one microcomputer controls travel functions (particularly, running, steering and stopping functions) which are fundamental functions of a vehicle, and that other microcomputers control functions other than the travel functions (e.g., functions associated with power supply to other devices and security).
Typical conventional electronic control apparatus with a microcomputer have been configured so that the apparatus will be provided with a monitoring circuit which monitors whether or not the microcomputer is in normal operation and, when malfunction is found, performs failsafe processes, such as initialization.
Meanwhile, an electronic control apparatus with integrated electronic control apparatuses having a plurality of microcomputers is disclosed, for example, in Japanese Patent Publication (Laid-open) No. 2007-041824. The electronic control apparatus disclosed in this reference is ensured to have a monitoring circuit for each of the plurality of microcomputers.
Let us assume a case where the technique disclosed in the above reference is applied to the above-mentioned electronic control apparatus in which one of the plurality of microcomputers controls travel functions of a vehicle and other microcomputers control the functions other than the travel functions. In such a case, the system will have a configuration where each of the microcomputers is provided with a monitoring circuit.
With this configuration, however, if malfunction occurs in the monitoring circuit for the microcomputer that controls the travel functions, monitoring will no longer be enabled as to whether or not the control is in good order for the particularly important travel functions of the vehicle.